Process of manufacturing tungsten anticathodes for röntgen tubes.



0. A. SIMPSON. PROCESS OF MANUFACTURWG TUNGSTEN ANTICATHODES FOR R O NTGEN TUBES.

APPLICATION FILED-FEB. 4. 1913.

1,167,532, Patented Jan. 11, 1916.

. M fi m/m UNITED STATES PATENT OFFICE.

OTTO ARCHIBALD SIMPSON, OF CHARLOTTENBURG, GERMANY, ASSIGNOR TO SIEMENS & HALSKE A. G., OF BERLIN, GERMANY, A CORPORATION OF GERMANY.

PROCESS OF MANUFACTURING TUNGSTEN ANTICATHODES FOR RONTGEN TUBES.

, Application filed February 4, 1913.

To all whom it may concem Be it known that I, O'r'ro ARCHIBALD SIMPSON, a citizen of the German Empire, and residing at Gharlottenburg, near Berlin, Germany, have invented a certain new and useful Improved Process of Manufacturing Tungsten A;nticathodes for Rontgen Tubes, of which the following is a specification.

.My invention relates to the manufacture of anti-cathodes for :Rtintgen tubes.

As is well-known, in Rontgen tubes it is desirable to form the anti-cathode mirror with a convex face in order, to keep down as much as possible the production of secondary cathode rays. The manufacture of a convex mirror when tungsten is used as the anti-cathode material involves considerable difliculties, however, as soon as an attempt .is made to obtain the convex face by mechanical treatment.

A primary object of my invention is to obviate the difliculties met with when making convex anti-cathodes of tungsten, and to this end I melt in the electric are a piece of tungsten, which may be either drawn tungsten or be formed by compressing to gether powdered tungsten and which corresponds to the anticathode to be obtained, and after melting the said piece I leave it to freely cool. In consequence of the great surface tension a body having a convex surface is obtained by this melting process, and a plano-convex or a biconvex piece of tungsten can be obtained according to the formof the support 'or foundation on which it rests.

In the drawings'which show the preferred embodiment of the invention, Figure 1 is a section of .the anti-cathode holder, the anticathode being shown in elevation supported thereby; Fig. 2 is a section of the cathode at one stage of its manufacture, the stem being shown in elevation prior to its fusion with the plate; Fig. 3 is a top plan View of the same.

In its preferred embodiment, the invention contemplates the rapid conduction of heat from the anti-cathode by providing it with a stem integraltherewith, said stem being adapted to mount the anti-cathode in the manner to be referred to. Preferably the following process is employed: A round plate ma'de'of tungsten metal powder under igh pressure is provided with a hole and after this plate is thoroughly fused in the Specification of Letters Patent.

Patented Jan. 11, 1916. S rial No. 746,241.

electric arc, around tungsten rod is fitted into the hole in such manner that its end protrudes slightly beyond the plate. Thereupon the plate is fused in the electric arc with the upper portion of the rod. When during this process the heating is extended over the whole plate and it is permitted afterward to chill off in the open, a body is formed having a convex surface owing to the large surface tension, such as is for instance known in the manufacturing of bodies of silver. By this process not only the anti-cathode plate is joined perfectly with the stem, but also a curved surface is obtained without any additional working, which has excellent qualities with regard to its density and smoothness.

As may be seen from Fig. 1, the cathode which is inserted into anti-cathode holder k (preferably a copper block) consists of a head plate p with a curved surface onto which a stem t is joined in such manner that the anti-cathode assumes a mushroom shape.

While the stem t secures a good dissipation of the heat into the copper block is this effect may be obtained in somewhat less perfeet manner, when the anti-cathode is freely mounted in the Rontgen tube; in which case, however, it is advisable to employ a stem with somewhat larger cross section.

In manufacturing, the anti-cathode is made of tungsten metal powder compressed under high pressure into a round plate 12 and as may be seen from Figs. 2 and 3 it is provided with a hole'or an opening. After the plate has been thoroughly fused in the electricarc a rod t of tungsten metal, preferably somewhat pointed at its end, is inserted into this hole so that it slightly protrudes beyond the surface of plate p. Then the plate and the stem are fused together in the electric arc and permitted to chill in the open, so that the form is obtained which is shown in Fig. 1.

the said piece and rod become welded together, and in allowing the molten mass no formed to cool freely. A

2. A process of making tungsten ant1- cathodes for R-ontgen tubes, consisting in melting a hole into a plate of tungsten formed of tungsten powder compressed together, in fitting in the hole the tapered end of a drawn rod of tungsten, in heatin said plate until the plate is 'melted an welded to the rod, and in allowing the molten mass so formed to cool freely.

3. The process of manufacturing an anticathode for Rontgen tubeswhich consists in compressing tungsten metal powder to form a plate, in providing said plate with a hole, in inserting a stem into said hole, and in fusing said stem to said plate.

4. The process of manufacturingan anticathode for Rontgen tubes which consists in compressing tungsten metal powder and fusing the same to form an integral plate, in providing a hole in said plate, in inserting a tungsten rod into said hole with its end protruding beyond the surface of said and in permitting the fused mass composed of the plate and rod end to become chilled while its surface is curved under the surface tension of the metal.

In testimony whereof I have signed my name to this specification in the presence of two witnesses.

OTTO AR-CHIBALD SIMPSON.

WVitnesses WOLDEMAR HAUr-T. HENRY HZSPER.

plate, in fusing the rod and plate together, 

